Physiologic Regulation of Lipid Oxidation and Ferroptosis By Vitamin E, High-Density Lipoprotein, and Scavenger Receptor Class B Type 1

Ferroptosis is a form of cell death caused by oxidative (-OOH) damage to phospholipids (PL) that comprise the cell membrane. Understanding mechanisms of ferroptosis is important because of the role it plays in human disease, including cancer and neurodegeneration. Previous work has focused on the intracellular antioxidant enzyme glutathione peroxidase 4 (GPx4), which detoxifies PL-peroxides (PL-OOH) and prevents ferroptosis. Studies also show that alpha-tocopherol (-toc), the active form of Vitamin E, is an exogenous lipophilic antioxidant that inhibits ferroptosis in cancer cells in vitro and in neurons and hematopoietic stem cells in vivo. The mechanisms by which -toc engages cells to manipulate PL redox balance and ferroptosis are unknown. Lipoproteins, like high- and low-density lipoproteins (HDL and LDL), carry -toc in the circulation, which compelled our investigation of their role in -toc delivery and ferroptosis. Using cancer and neuronal cell models, here we show that lipoproteins, particularly HDL, deliver -toc by binding the cell membrane receptor scavenger receptor class B type 1 (SR-B1) to prevent ferroptosis. Additionally, we synthesized SR-B1 targeted HDL-like particles that contained -toc to validate data obtained with native lipoproteins. We reveal here a tunable cellular redox axis whereby native and synthetic HDLs containing -toc target SR-B1 to reduce PL-OOH and prevent ferroptosis.